This invention relates to an absorbent structure having a water-repellent, nonwoven fabric facing in combination with wicking fibers in an absorbent batt.
Absorbent structures such as disposable diapers have been well accepted by consumers because they provide substantial advantages from the standpoint of convenience. Most disposable diapers incorporate three basic elements into their construction: a water-impervious backing sheet, a water-permeable facing sheet, and an absorbent batt situated between the facing sheet and the backing sheet.
One advantage which disposable diapers may have over non-disposable cloth diapers is that the multilayer disposable diaper, such as the one disclosed in U.S. Pat. No. 3,612,055 to Mesek et al, may be constructed so that when an infant voids into the diaper, the absorbent batt layer will absorb and retain the urine, while the facing sheet which is situated next to the infant's skin remains dry. To accomplish this result, the facing sheet must be less wettable than the absorbent batt. However, the facing sheet must be sufficiently wettable, as opposed to being water repellent, to permit the excreted body fluids to permeate through the facing sheet and into the absorbent layer behind it.
One method for construction of a facing sheet is from short length cellulosic fibers, such as wood pulp fibers or cotton linters or the like, as is disclosed in U.S. Pat. No. 3,633,348 to Loloia et al. Facing sheets so constructed are less expensive than woven fabrics, and thus are suitable for use in disposable diapers. The method of preparing this bonded nonwoven facing sheet includes the steps of forming a web of randomly laid dry fibers, impregnating the web with a binder and a surfactant, and drying the web to form the facing sheet. The surfactant is included in the steps of impregnating the web with the binder in order to offset the water-repellency which the binder imparts to the normally cellulosic fibers. The wettability of the nonwoven facing sheet can be controlled by the amount and placement of addition of a surfactant. However, as the wettability is increased, the water-repellency is decreased.
Another approach to the problem is the method disclosed in U.S. Pat. No. 3,730,184 to Mesek. In this method, a nonwoven facing sheet is prepared having a controlled degree of wettability in which the central portion of a web of randomly laid dry fibers is treated with a binder and a surfactant, while the marginal portions of the web are treated with binder material alone. In this manner the central portion is more wettable, whereas the surrounding portions are substantially water repellent.
Other absorbent structures, such as those used for absorbing body exudates, having a facing sheet and an absorbent batt, are catamenial devices, wound dressings, incontinence pads and the like.
It would be most desirable to provide a nonwoven facing sheet wherein the high water-repellency is retained and a means is provided for the liquid to penetrate the facing sheet to be absorbed by the absorbent panel below.